39. Appendix A: PostGIS Functions¶
39.1. Constructors¶
- ST_MakePoint(Longitude, Latitude)
Returns a new point. Note the order of the coordinates (longitude then latitude).
- ST_GeomFromText(WellKnownText, srid)
Returns a new geometry from a standard WKT string and srid.
- ST_SetSRID(geometry, srid)
Updates the srid on a geometry. Returns the same geometry. This does not alter the coordinates of the geometry, it just updates the srid. This function is useful for conditioning geometries created without an srid.
- ST_Expand(geometry, Radius)
Returns a new geometry that is an expanded bounding box of the input geometry. This function is useful for creating envelopes for use in indexed searches.
39.2. Outputs¶
39.3. Measurements¶
- ST_Area(geometry)
Returns the area of the geometry in the units of the spatial reference system.
- ST_Length(geometry)
Returns the length of the geometry in the units of the spatial reference system.
- ST_Perimeter(geometry)
Returns the perimeter of the geometry in the units of the spatial reference system.
- ST_NumPoints(linestring)
Returns the number of vertices in a linestring.
- ST_NumRings(polygon)
Returns the number of rings in a polygon.
- ST_NumGeometries(geometry)
Returns the number of geometries in a geometry collection.
39.4. Relationships¶
- ST_Distance(geometry, geometry)
Returns the distance between two geometries in the units of the spatial reference system.
- ST_DWithin(geometry, geometry, radius)
Returns true if the geometries are within the radius distance of one another, otherwise false.
- ST_Intersects(geometry, geometry)
Returns true if the geometries are not disjoint, otherwise false.
- ST_Contains(geometry, geometry)
Returns true if the first geometry fully contains the second geometry, otherwise false.
- ST_Crosses(geometry, geometry)
Returns true if a line or polygon boundary crosses another line or polygon boundary, otherwise false.